On account of the fact that in such an elevator system several elevator carriages can be moved largely independent of one another in a common shaft of the shaft system, the problem with such elevator systems is to ensure that a collision between the adjacent elevator carriages is reliably avoided.
To this end, it is normally necessary for a plurality of operating parameters of an elevator system to be recorded and analyzed, in particular the current position of each elevator carriage. The more elevator carriages an elevator system has, the more complex becomes the amount of data that has to be processed and transmitted.
An elevator system with at least one shaft in which at least two elevator carriages can be moved along a common transportation route is known from the document EP 1 562 848 B1. In this elevator system, the elevator carriages are each assigned a control unit, a drive unit and a brake. In order to prevent a collision between the elevator carriages of the elevator system, the distance between adjacent elevator carriages is respectively monitored. If a specified critical minimum distance is fallen short of, it is envisaged that an emergency stop of the elevator carriage be triggered.
A further elevator system in which a plurality of elevator carriages can be moved simultaneously in at least one shaft is known from document EP 0 769 469 B1. In this elevator system, each elevator carriage has its own drive unit and its own safety module. The safety modules are hereby designed to trigger the brake system of the respective elevator carriage as well as of other elevator carriages. To this end, it is envisaged that data recorded and/or analyzed by one safety module be transmitted to all other safety modules. One problem known from EP 0 769 469 B1 is that the amount of data to be transmitted is so large that a constant transmission and analysis of this data by the safety modules is not possible, at least not with a reasonable technical effort, which is why EP 0 769 469 B1 suggests working with a dynamic elevator model.